EXTENSOR POLLICIS LONGUS

ORIGIN
Middle third of posterior ulna (below abductor pollicis longus) and adjacent interosseous membrane
INSERTION
Base of distal phalanx of thumb via Lister's tubercle (dorsal tubercle of radius).
ACTION
Extends interphalangeal and metacarpophalangeal joints of thumb
NERVE
Posterior interosseous nerve (C7 , 8 )